Piston for internal-combustion engines having acoustic detonation suppression means



Dec. 15, 1953 300mg, JR 2,662,517

PISTON FOR INTERNAL-COMBUSTION ENGINES HAVING ACOUSTIC DETONATION SUPPRESSION MEANS Filed March 1, 1952 Patented Dec. 15, 1953 PISTON FOR INTERNAL-COMBUSTION EN- GINES HAVING ACOUSTIC DETONATION SUPPRESSION MEANS Albert G. Bodine, Jr., Van Nuys, Calif. Application March 1, 1952, Serial No. 274,421

9 Claims. 1

This invention relates generally to internal combustion engines and to means for suppressing irregular burning and detonation of fuel-air mixture therein. The invention is based on my discovery that detonation in combustion engines involves acoustic phenomena and can be alleviated by means of certain acoustic apparatus used in combination with the combustion chamher.

The present application is directed to improvements in the field covered by Patent No. 2,573,536, issued October 30, 1951, and entitled Engine Detonation Control by Acoustic Methods and Apparatus. For a full discussion of the acoustic aspect of detonation in combustion, and my basic solution for controlling detonation in combustion, reference should be had to my said issued patent.

Only briefly stated herein, the present invention is based on the fact that detonation in an engine combustion chamber produces sound waves, a large part of which rise to high amplitude at resonant frequencies of the chamber, and on my discovery that the sound Waves produce some of the various well-known and harmful 1 manifestations of detonation. According to my basic invention, I inhibit or attenuate these harmful effects by interfering with or attenuating the high amplitude, detonation-induced sound waves, and this is done by use in connection with the combustion chamber of acoustic attenuation means made responsive to (operable at) the frequencies at which the detonation-induced sound waves build up to high amplitudes. One type of acoustic attenuation means broadly disclosed in my patent involves an attenuative configuration given to the upper end portion of the piston.

The general object of the present invention is the provision of an improved detonation controlling sound wave attenuator means of the class involving the piston structure.

A further object is the provision of a novel piston type detonation attenuator which has good frequency response characteristics to the frequency range at which oifensive detonation is encountered.

An illustrative embodiment of the invention is shown in the drawings, wherein:

Figure 1 is a perspective view of a piston provided with detonation attenuative means in accordance with the invention;

Figure 2 is a reduced plan view of the piston of Figure 1;

Figure 3 is an elevational view of the upper end portion of the piston, shown together with a 2 fragmentarily illustrated cylinder and combustion chamber;

Figure 4 is a developed view of the sound wave attenuative upper end portion of the piston, be-

ing taken as represented by the line ii- 3 of Figure 2; and

Figure 5 is a fragmentary section looking vertically downward along the line 55 of Figure 1. 1

The attenuator of the present invention is of a type, first disclosed in my said issued Patent No. 2,573,536, employing an exponential type horn, which is designed to receive the offensive detonation-induced sound waves without reflection back, and to conduct such waves to a sound wave attenuative means at its throat. Such a horn must be properly designed to respond to the wave frequencies to be subdued, and information on this subject is found in my said issued patent. According to the present invention, such a horn and attenuative means is provided by a unique configuration of the upper end portion of the piston.

Referring now to the drawings, the numeral i0 designates generally a piston, having conventional grooves H for piston rings, not shown. Above uppermost ring groove ii, the piston has a. small reduction in diameter, forming a land 52, at a small clearance distance from the cylinder wall, represented at 13 below combustion chamber space 53a. This clearance space, indicated with exaggeration at it, may typically be of the order of 0.005", although this dimension is not critical. Sunk into land [2 are a plurality of helically formed horn slots 9 5, each opening through the top surface of the cylinder, and each, in the illustrative embodiment, extending helically about the piston for a distance of approximately In the present illustrative embodiment, there are eight of such horn slots, equally spaced about the piston and overlapping one another by angular extents of approximately 90. The slots have a cross-sectional area which converges in the helically downward direction in the manner of exponential type horns. According to the illustrative embodiment, this is achieved by making the slots of constant width but diminishing depth in the downward direction. At their lower ends the slots thus pinch out to zero crosssectional area, as may be seen best in Figure 5. At their upper ends, on the contrary, the slots have wide mouths is, spaced from one another by the narrow areas at i9, so that the large ends or mouths of the helical horn passages or slots [8 occupy a large portion of the periphery of ends or mouths [8 of the horn slots, and travels down and around said slots toward the reduced lower ends thereof. A well known acoustic char} acteristic of an exponential'hor'n passage, such as afforded by the slots 15, is the ability to transmit the sound wave from the mouth of the passage to the constricted throat without reflection back. The sound waves received by the horn slots accordingly travel down and around the horn slots. Owing to the fact that the horn slots are open-sided, however, a portion of the sound wave spills out of the horn slots into the clearance space Hi all along the length of the slots. The sound wave diverted into the narrow clearance space 14 is rapidly and effectively dissipated, and its energy converted to heat.

It is, of course, necessary in any given engine to determine first the frequency of the detonation sound wave which is to be subdued. The horn passages or slots l5 may then, with this information, and in accordance with the teachings set forth in my aforesaid issued Patent No. 2,573,536, be properly designed to accept, without reflection back, sound waves of the offensive detonation frequency range, and to dissipate these waves all along the length of the horn slots by spilling them into the narrow clearance space I4, as aforesaid.

It should here be mentioned that while a true exponential horn shape is here principally referred to, some deviation from a true exponential curve is, in practice, quite permissible Without loss of the substantial benefits of the invention. Horn shapes of catenoidal or hyperbolic form are useful, and other equivalent shapes are also feasible. In general, the broad requirement is that the horn be of the usual flared type used for coupling purposes in acoustic practice.

It will be understood that the drawings and description are illustrative only, and that various changes in design, structure and arrangement may be made without departing from the invention as defined by the appended claims.

I claim:

1. For use with an internal combustion engine having a cylinder opening into a combustion chamber, a piston adapted for reciprocation in said cylinder, said piston having at its upper end a slightly set back surface furnishing a clearance space with the opposed wall of the cylinder, and having sunk into said surface a groove, one side of which opens into said clearance space, the upper end of said groove opening through the 4 top of the piston to the combustion chamber, and the cross-sectional area of said groove converging downwardly in the manner of a flared acoustic horn.

2. The subject matter of claim 1, wherein the cross-sectional area of the groove converges in a downward direction substantially in the manner of an exponential horn.

3. The subject'matte'r of claim '1, wherein the mouth of the groove opens through the top edge of the piston, and the groove extends from said mouth both downwardly and circumferentially around the piston.

.4; 'I'hesubject matter of claim 1, wherein the width of the groove is substantially constant and its depth is gradually reduced in a downward direction.

" 5.' For use with an internal combustion engine having a cylinder opening into a combustion chamber, a piston adapted for reciprocation in said cylinder, said piston having at its upper end a. slightly reduced, substantially cylindrical portion extending therearound furnishing a clear ance space with the opposed wall of the cylinder,

and having sunk into the surface of'said portion a plurality of grooves, the upper ends of which open through a peripheral portion of the top of the cylinder and are circumferentially spaced thereabout, said grooves extending downwardly and helically around said cylindrical portion of said piston, each at least partially overlapping portions of adjacent slots in the'circumferential direction about the piston, the cross-sectional area of each of said grooves converging helically downwardly in the manner of a flared acoustic horn, and each of said grooves opening along its length into said clearance space.

6. The subject matter of claim 4, wherein said grooves converge substantially in accordance with an exponential function.

7. The subject matter of claim 4, wherein the widths of the grooves are substantially constant and the depths thereof gradually diminish in the helically downward direction.

8. The subject matter of claim wherein said grooves converge substantially in accordance with an exponential function wherein the widths of the grooves are substantially constant and the depths thereof gradually diminish in the helically downward direction.

9. For use with an internal combustion engine having a cylinder opening into a combustion chamber, a piston adapted for reciprocation in said cylinder, said piston having sunk into the outer side surface of its upper end portion a groove, the upper end of which opens through the top of the piston to the combustion chamber, and the cross-sectional area of which converges in a downward direction in the manner of a flared acoustic horn.

ALBERT G. BODINE, JR.

No references cited. 

